The present invention relates to a fuel injection device for an internal combustion engine, and particularly to a fuel injection device for an internal combustion engine in which a fuel injected from a fuel injection port is prevented from adhering to the interior wall surface of an intake pipe.
Recently, environmental issues concerning automobiles have been given much attention. Therefore, to improve exhaust gas performance and fuel consumption of internal combustion engines, a variety of internal combustion engines such as lean burn engines and direct injection engines have been proposed.
The direct injection engine is an internal combustion engine that injects fuel directly into a combustion chamber. However, the direct injection engine is disadvantageous in that the piston head needs to be in a special shape, and peripheral devices are required for direct injection of fuel. Further, many modifications must be made to an existing base engine, leading to a higher production cost for the internal combustion engine.
Accordingly, development of a lean burn engine having a multipoint injection system (MPI system) comprising a fuel injection valve in the vicinity of an intake port of each cylinder of the internal combustion engine has been proposed. The lean burn engine is an internal combustion engine in which a gas mixture made lean is brought into combustion. In the lean burn engine, fuel injection is carried out synchronously with the intake stroke, thereby achieving a leaner mixture gas while collecting an ignitable rich gas mixture only around an ignition plug, whereby it is possible to realize improvements in fuel consumption and exhaust gas performance of the internal combustion engine. Further, in order to realize improvements in the fuel consumption and exhaust gas performance of the internal combustion engine, it is necessary that the particle size of the fuel droplets injected by a fuel injection device not be greater than about 70 xcexcm.
Conventionally, for realizing improvements in the combustion of a lean burn internal combustion engine comprising the above-mentioned MPI system, various proposals have been made. For instance, reducing the particle size of the injected fuel by providing a multiplicity of holes at the injection port portion of the fuel injection device or injecting the fuel at a central portion of an intake port by forwardly projecting the injection port portion (formation of long nozzle). But the reduction of the particle size of the injected fuel has the drawback that the smaller particulates of the injected fuel have smaller mass as compared with injected fuel of ordinary particle size, and are more susceptible to influence of air flow, so that the flow of the injected fuel is directed and adheres to the interior wall surface of the intake pipe.
As shown in FIGS. 16, 17, the spray of fuel injected from a fuel injection valve 1 into the air flow in the intake pipe 18 is largely deflected in the air flow direction, resulting in the fuel adhering to the interior wall surface 18a of the intake pipe 18. The quantity of the fuel adhered depends on the temperature of the intake pipe 18, particle size of the fuel droplets, flow rate of air and the like. In FIG. 16, an air control valve 40 and a throttle valve shaft 41 is provided to regulate the flow of air in the main air passage. But, as this prior art still has the drawback of fuel particles adhering to the interior wall surface 18a. 
Also, as shown in FIG. 18, the particle size of the spray of the fuel injection valve 1 is reduced, and the spray point is disposed nearer to the intake valve (nozzle is elongated) for the purpose of preventing the adhesion of fuel particles to the wall surface. But, in the case of FIG. 18, the fuel particles adhere to the interior wall surface 18a of the intake pipe.
The present invention provides a fuel injection device for an internal combustion engine which resolves the problem of adhesion of fuel particles to the internal wall surface of the intake pipe, in order to improve the quality of gas mixture in a cylinder.
In an object of the invention a fuel injection device is provided comprising an intake pipe having interior wall surfaces for providing air from an upstream side to a downstream side and a fuel injection port disposed in the intake pipe between the surfaces for providing fuel into the intake pipe. Further, the invention provides an air guide member disposed in the intake pipe in a plane substantially parallel to the surfaces for guiding air separately towards an air flow layer passage and a main air passage wherein the air guided towards the air flow layer passage has a speed at least greater than the air guided towards the main air passage.
In another object of the invention an engine is provided comprising an engine control unit and a fuel injection device electrically coupled to the engine control unit for regulating fuel injection, the device comprising an intake pipe having interior wall surfaces for providing air from an upstream side to a downstream side and a fuel injection port disposed in the intake pipe between the surfaces for providing fuel into the intake pipe. The invention further provides an air guide member disposed in the intake pipe in a plane substantially parallel to the surfaces for guiding air separately towards an air flow layer passage and a main air passage wherein the air guided towards the air flow layer passage has a speed at least greater than the air guided towards the main air passage.
In yet another object of the present invention a fuel injection device is provided comprising an intake pipe having interior wall surfaces for providing air from an upstream side to a downstream side and a fuel injection port disposed in the intake pipe between the surfaces for providing fuel into the intake pipe. The invention further provides an air guide member disposed in the intake pipe in a plane substantially parallel to the surfaces for guiding air separately towards an air flow layer passage and a main air passage wherein the air guided towards the air flow layer passage has a speed at least greater than the air guided towards the main air passage wherein the air flow layer passage on the upstream side has a greater cross sectional area than the air flow layer passage on the downstream side.
In another object of the present invention an engine is provided comprising an engine control unit and a fuel injection device electrically coupled to the engine control unit for regulating fuel injection, the device comprising an intake pipe having interior wall surfaces for providing air from an upstream side to a downstream side and a fuel injection port disposed in the intake pipe between the surfaces for providing fuel into the intake pipe. The invention further provides an air guide member disposed in the intake pipe in a plane substantially parallel to the surfaces for guiding air separately towards an air flow layer passage and a main air passage wherein the air guided towards the air flow layer passage has a speed at least greater than the air guided towards the main air passage wherein the air flow layer passage on the upstream side has a greater cross sectional area than the air flow layer passage on the downstream side.
In yet another object of the present invention an intake pipe having interior wall surfaces for providing air is provided comprising an air guide member disposed in the intake pipe in a plane substantially parallel to the surfaces for guiding air separately towards an air flow layer passage and a main air passage wherein the air guided towards the air flow layer passage has a speed at least greater than the air guided towards the main air passage for guiding an injected fuel away from the surfaces.
In another object of the present invention an engine is provided comprising an engine control unit and an air intake control unit coupled to the engine control unit for regulating air intake, the air intake control unit being coupled to an intake pipe having interior wall surfaces for providing air. The intake pipe comprises an air guide member disposed in the intake pipe in a plane substantially parallel to the surfaces for guiding air separately towards an air flow layer passage and a main air passage wherein the air guided towards the air flow layer passage has a speed at least greater than the air guided towards the main air passage for guiding an injected fuel away from the surfaces.